My friend is a slut. What do I do?!

Okay, my friend is a total slut, sleeping with guy after guy.
I'm worried to death about her.
People have told me that I can't change a person,
that, talking to her about the fact that the entire school knows she's a slut won't make her
change.
Is that true?
I mean, if you see a person messing up their life because their homelife is shit
would you stay silent?
I'm still friends with this girl even though most of my friends have dropped her.
Hell, she even stole my crush (and she knew I liked him).
She complains sometimes that all girls are bitches only because none want to be her friend.
Except me.
Strait up, people don't like being friends with sluts.
But, I'm still her friend because....
I'm worrried.
I don't think shes suicidal.
What i do know is that she will, however, do whatever she can for attention.
It's easy to see that her mother doesn't love her.
And her stepdad is a jackass.
But after a year of this...
I don't know.
She's a lot more of a bitch this year, this i know.
But, I don't know if i should give up on her...
What would you do?